Air-conditioning units help protect small children, the elderly and pets from the effects of extreme heat — but some doctors are worried that they can also cause health issues.

“They do have benefits in terms of [protecting us from] air pollution and particularly in times of heat waves, but they’re not without risk,” said Dr. Farah Shroff. Shroff is a public health researcher and professor at the University of British Columbia.

“The main concern with indoor air conditioning systems is that they need to be well maintained to reduce the risk of microbial contamination,” which is defined as the accidental introduction of microbes such as bacteria, yeast, mold and fungi.

“If the building’s systems aren’t maintained properly, you can get a buildup of bacterial pathogens which can cause illnesses such as Legionnaires’ disease (a severe form of pneumonia) or Pontiac fever,” said Tadiboyina.

“[Bacterial pathogens] can also cause a runny nose, sore throat and allergic reactions.”

The problem, said Tadiboyina, is that these symptoms are caused by several different illnesses, making it tricky for doctors to say definitively whether your air conditioner is the issue.

“Oftentimes, when [patients] come in with respiratory symptoms [such as] fever, fatigue, coughing, wheezing… these kinds of things are non-specific symptoms,” he said.

Fortunately, the more severe illnesses — like Legionnaires’ disease — are identifiable with further testing.

If you are experiencing any of these symptoms, you should see a doctor.

‘Sick Building Syndrome’

A study published in the International Journal of Epidemiology in 2004 found that people who worked in air-conditioned office buildings were more likely to become sick than those who worked in buildings without central air.

Researchers, who compared buildings with air conditioning to buildings with natural ventilation, referred to this phenomenon at “Sick Building Syndrome” (SBS).

Lead researcher Dr. Mark J. Mendell said one possible explanation for the increase in illness is “the moisture in AC and humidification systems.” Mendell feared that moisture can result in “in microbiological exposures that cause health effects through mechanisms that are irritant, toxic or allergic.”

Little research has been done on SBS, but Shroff — who isn’t an expert on the condition — said a poorly maintained AC unit in a large building could cause issues for the people who live or work there.

“If the air conditioning is not well-maintained… a large number of people in that building could be impacted,” she said. “It’s not just our air conditioning. It’s a syndrome that has been shown to cause health problems related to air quality.”

Shroff clarifies that natural ventilation would only be better than air conditioning if pollution levels were low. “It really depends on what’s going on with outside air,” she said.

In extreme heat, AC offers more benefits than pitfalls

Both Tadiboyina and Shroff believe the benefits of air conditioning outweigh the risks — especially during periods of extreme heat.

“Extreme heat is very dangerous,” said Tadiboyina. “It may not be as dangerous for young, healthy people… but there is a subset of the population that is very susceptible to heat.”

Tadiboyina said people with cardiovascular disease, physical disability and those who have previously had a stroke are at a higher risk for heat exhaustion and heat stroke.

Extreme heat is also more dangerous for people who abuse alcohol, cocaine or other stimulants, as well as anyone who takes beta blockers, diuretics or cold medication on a regular basis. “Air conditioning can offset this risk,” he said.

Another 2011 study from Yale University supported Tadiboyina’s claims. In it, researchers found that the use of air conditioning lowered the risk of hospitalization and death from cardiovascular disease and other issues in people age 65 and older.

WATCH BELOW: How will climate change affect Canada?

Shroff believes access to air conditioning during extreme heat is a matter of equality.

“When people are dying from heat stroke, the benefits [of air conditioning] outweigh the negative aspects,” she said. “We need to make sure that everyone has access to it.”

You should have your AC unit serviced at least once a year

Craig Goettler is the chief operating officer at Right Time Heating and Air Conditioning. He said that yearly service will ensure there isn’t any stagnant water in the evaporator coil of your air conditioner.

The evaporator coil is the part of your AC unit which absorbs the heat and humidity from the air in your house. If your evaporator coil has been collected moisture and then the moisture remains in place, mold will quickly grow.

“All the air that goes through your home flows over and out your evaporator coil,” Goettler said. “If you have mold buildup, you will have more being spread throughout your home.”

He also cautioned against leaving the same filter in your furnace throughout the summer months.

“We are seeing people not changing their furnace filter [because] the furnace isn’t heating… but it’s still blowing the air through your system,” he said. If you let the filter collect dust, dust will be blown into the air that you breathe.